Device and method for identifying an object in or on a closable opening

ABSTRACT

The invention relates to a device and a method for identifying an object O in an opening that can be closed by means of a mobile element ( 12 ). Light is fed into at least one fiber-optic light guide ( 33, 34 ) from a light source ( 1, 2 ), and variations in the received light are detected by means of at least one receiver (Ea, Eb), the fiber-optic light guide being arranged at least partially along the edge of the opening ( 11 ). A first fiber-optic light guide sends light transversally to the length thereof, said light being then received by a second fiber-optic light guide transversally to the length thereof. The second fiber-optic light guide ( 34 ) is connected to the receiver (Eb). The fiber-optic light guides are arranged on the edge of the opening ( 11 ) in such a way that a light field (F) at least partially bridging the opening is produced. At least one light source ( 1, 2 ) and at least one receiver (Ea, Eb) are respectively associated with each fiber-optic light guide ( 33, 34 ), and a clock circuit is used to alternately feed the light received by the respective receiver into the fiber-optic light guides. Comparison means are used to compare the signals on the receivers in order to identify the object.

REFERENCE TO RELATED APPLICATIONS

The present application claims the priority of the German patentapplication 10 2004 025 345, filed on May 19, 2004, the disclosurecontent of which is also expressly made the subject of the presentapplication.

1. Field of the Invention

The invention relates to a device and a method for identifying an objectin or on a closable opening according to the preamble of claims 1 and17.

2. Prior Art

As soon as a movable part in a guide moves toward another part, there isbasically the risk that an object located in between will be jammed in.Examples of this are found not only, but also, in the vehicle sectorwhen, for example, a window closer or a sliding roof closes, inparticular when this closing takes place automatically by means of amotor drive, or when a vehicle opening such as a door or a boot lid isclosed.

Problems of this type were generally solved up to now in that therelevant space region is monitored according to the light barrierprinciple. If an object is located between the optical transmitter, suchas for example an LED, and the optical receiver, such as, for example aphotodiode, light is absorbed and the total quantity of light at thereceiver is reduced. The evaluation electronics identify with the aid ofthis change in the light quantity received, that an object is presentand relays this information to the higher-order processing unit. If itis desired to monitor the passage of objects through an area in thespace, a plurality of such light barriers may be arranged next to oneanother.

Alternatively, the light expansion can be concentrated on the area to bemonitored by means of a suitable transmitting and receiving opticalsystem, such as is known from WO 03/009476 A1. It is thereby possible toilluminate the region to be monitored in a planiform manner with onlyone light source and only one receiver. If necessary, the sensitivityregion in the direction perpendicular to this surface can be keptnarrow, so that false triggerings by objects outside the passage areaare minimised.

According to the jamming protection regulations, such as are available,in particular for sliding roofs, requirements are set for the protectionof occupants by legislation for automatic closing functions, such as,for example, automatic closing or remote closing, it not being possibleto meet these requirements to an adequate extent/in conformity with thelaw with conventional jamming protection solutions, for example in theform of an indirect jamming protection. This situation intensifies inthe case of the “externally running sunroofs” which are also calledpanorama roofs. Owing to the design structure, these roofs present amuch greater danger potential with regard to the risk of jamming in,which cannot currently be completely covered in conformity with the lawwith conventional measures. The synchronous running variations, causedby the design, of the externally running sun roofs and the possiblelarge spread of the mechanical tolerances lead conventional jammingprotection systems to the limit of detection possibility.

Light guides have already been used in the area of sliding roofs forjamming protection. In this regard, DE 102 05 810 A1, on which thepreamble of claim 1 is based, suggests the use of a light guide, whichis deformed under the action of an external pressure, so the intensityand/or the frequency and/or the running time of a light fed into thelight guide is influenced. Owing to this change, it is concluded thatjamming in has taken place and the drive of the sliding roof iscorrespondingly actuated. The optic-fibre light guide is arranged alongthe frame of the opening and can have a reflective coating at one end.

An arrangement of at least two light-emitting diodes is known from EP 0706 648 B1, which act in an alternating manner on a photo receiver. Thelight controlled with respect to the amplitude of at least one lightpath acts together with the light of a further light source on the photoreceiver in such a way that a receiving signal is produced withoutclocked signal fractions. The receiving signal of the photo receiver issupplied to a synchronous demodulator which in turn separates thereceiving signal into the two signal components according to the lightsources. The two signal components are compared with one another afterlow-pass filtering in a comparator. If signal differences occur, theseare adjusted to zero by means of output control of at least one of thelight sources, in order to thus achieve extraneous light compensation,in particular.

In the vehicle area, there is the added difficulty, however, that thereceivers are so far apart from one another, under some circumstances,that they are subjected to significant temperature differences which canonly be managed with difficulty even with reference values.

DISCLOSURE OF THE INVENTION

Proceeding from this prior art, the present invention is based onproviding a device and a method for identifying an object in a closableopening, which operates reliably without contact.

This object is achieved by a device with the features of claim 1 and bya method with the features of claim 17.

Arranged at the edge of the opening are light guides, into which lightis fed, which is radiated transversely to the longitudinal extent of thelight guide from one light guide and is captured by the other lightguide. A light field is thus formed, which bridges the opening. The twolight guides are used alternately as emitting light guides and receivinglight guides, so a bidirectional light field is produced. An objectwhich is present in this bidirectional light field is identified by acomparative measurement between the signals received at the respectivereceivers. Owing to the structure of the light field, a favourablesolution is provided, as basically only a few receiving and transmittingelements have to be used in connection with the light guides. Thecomparative measurements allow reference values to be basicallydispensed with. Nevertheless, by corresponding evaluation of the valuesdetermined, both dynamic changes and an object statically located in thelight field can be detected. The latter especially is often a risk inthe previous systems, as it has to be identified, for example, in thecase of a window or sliding roof whether a hand has been located for arelatively long time in the opened aperture.

For effective protection of the occupants with respect to potentialjamming risks and for protection with respect to possible productliability claims, an optical light field is produced, for example in asliding roof in the roof liner aperture, which reliably detectspenetration and discontinues the automatic closure according to thelegal requirement, so a jamming situation is avoided.

The optical layers, generally light guides, can be concealed by the roofliner and are therefore not visible to the customer, if this is notdesired. The jamming protection can also be expanded to the control ofblinds. To increase the reliability of the system and to suppress falsetriggerings, a bidirectional light field is therefore used, preferablyin the multiplex method, with which possible false interpretations,owing, for example, to reflections as a result of the sliding roof coveror, in general, of the movable part, can be eliminated. At the sametime, the action of extraneous light can be better differentiated bythis arrangement.

The light guides can be economically arranged in the surface cover ofthe entire opening region, the light guide preferably being changedmechanically such that at many predefined locations light exits in atargeted manner and at a defined angle and the desired lightdistribution of the light field is produced over the opening. The lightguides are used in an alternating manner as transmitters and receivers.The mechanical change of the light guide brings about an elimination ofthe total reflection and therefore the output of light. Each outputlocation acts like a light source with a known radiation angle. Thenumber of output points, their position and the numerical aperture canbe varied in a targeted manner and determine the light distribution ofthe light field.

The signals present at the various receivers are preferably multipliedand/or divided, and/or their difference generated, in order to carry outdynamic and static measurements. The degree of efficiency of theprotection device can be increased in that the light guides have astructure which outputs the light transverse to their longitudinalextent from the light guide. This structure can preferably be present,augmented or reinforced, in the proximity of the closing region, so anincreased detection sensitivity exists there.

The light of the light guides can be emitted in the visible range inorder to achieve ambient illumination thereby. A light ring would beproduced, for example in the case of a sliding roof, in the lineraperture for the sliding roof. The compensated light information can beevaluated by means of the receivers, in particular in the case ofextraneous light compensation. The position of the sun can thus beidentified, for example, and the values determined thereby can be usedfor climate control or for control of a blind to reduce heating. Alltypes of light identification are therefore possible, so, for example,the interior lighting can be switched off in daylight and this leads, inparticular during stationary operation of the vehicle, to a reduction inthe power requirement.

In the same context, the light information can also be used formonitoring, in that incident light is used as useful information formonitoring of the interior or monitoring of the side windows.

The jamming protection is so sensitive that automatic control inconformity with the law is also possible without a line of sightconnection having to exist to the vehicle. Thus, the vehicle caninitiate automatic closure of the blind during insolation and remoteclosing is possible even at large ranges. Even small signals, such asthe signals from raindrops can be used as useful information, so rainclosure becomes possible. In this case, the light field detects rain andcauses automatic closing, for example of a sliding roof or window.

Advantageous configurations of the invention are provided in thecorresponding sub-claims and the following description.

SHORT DESCRIPTION OF THE FIGURES

Embodiments of the invention are described in more detail with the aidof the accompanying drawings, in which:

FIG. 1 shows the basic structure of a light field,

FIG. 2 shows the light field in side view,

FIG. 3 shows a schematic view of bidirectional measurements with a viewof the light flux of exponential characteristic of the light intensity,

FIG. 4 shows the signal course with the sliding roof closing with anabsorbing object superimposed in the light field,

FIG. 5 shows object identification by evaluation of the signaldifference,

FIG. 6 shows an associated circuit,

FIG. 7 to 10 show various alternative, schematically shown arrangementsof a light source, receiver and compensation element,

FIG. 11 shows an alternative schematically shown arrangement formultiple measurements,

FIG. 12 shows a transmitting/receiving characteristic of the lightintensity in the region of the closing edge,

FIG. 13 shows the static and dynamic signal course at the closing edgein the presence of an object over the time.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be described in more detail by way of examplewith reference to the accompanying drawings. However, the embodimentsare only examples which are not intended to limit the inventive conceptto a specific arrangement.

The Figures show a device for identifying an object in or on a closableopening 11, in particular the opening of a vehicle. Basically, in aclosable opening, it is to be identified whether an object O is locatedinside the opening, so a closing movement can optionally bediscontinued. During this identification, on the one hand, short-termchanges are to be identified, on the other hand, however, objects O thatare located longer-term in the opening also have to be identified.Openings of this type may be doors, windows, or, on a vehicle, windows,a sliding roof or boot. While, in the case of, in particular, motordriven movable parts on the vehicle, such as the sliding roof or awindow closer, mostly jamming and/or shearing movements of body types ofthe occupants are to be prevented, in the case of a boot lid it maymerely be a case of ensuring that no objects are located in the regionto be monitored. If, for example, in the case of a convertible vehicletop, the boot is automatically closed, no bottle or other item ofluggage should project into the closure region. Basically, the deviceand the method can also be used outside the vehicle area, however.

FIG. 1 shows the basic structure to generate a light field. By means ofa light source 1, light is fed into a first light guide 33 and isdeflected there on a structure 40 at an angle, which allows the light tobe emitted transversely to the light guide. It has been found that anoptimal narrow range is achieved in the case of a slightly angledarrangement is achieved according to the lines 52 and 53. For thispurpose, the emitting first light guide 33 in FIG. 1 and the receivingsecond light guide 34 have a structure 40 of this type. Light can eitherimpinge directly on this structure and be radiated or can further bedeflected according to the light path 54 on the first structure at anangle such that it is relayed within the total reflection in the lightguide and then, however, output at a further location of the structure.This is basically known from the earlier German patent application DE 102004 011 780.2.

The light received by the receiving second light guide is conducted tothe receiver Ea. If, according to FIG. 2, an object O arrives in thelight field F created in this manner, this leads to shadowing, which isperceived at the receiver Ea, Eb. According to FIGS. 3 and 6, at leastone light source 1, 2, 3, 4 and at least one receiver Ea, Eb ispreferably associated with each light guide, in each case. However, areceiver and light source do not have to be associated with each lightguide, it is also sufficient to only provide some of the light guidesaccordingly with a receiver and light source. It is only necessary forcorresponding transmission and, if necessary, compensation paths to beconstructed in the light field F, which will be dealt with below. If thelight guides consist of a plurality of segments, for example, a receiveror transmitter does not have to be associated with each segment. In thiscase, for example, a receiver or a light source can “service” aplurality of segments.

By means of a clock circuit 13, light is fed in an alternating mannerinto the light guides 33, 34 and is received by the respective receiver.Comparison means are provided, which compare the signals present at thereceivers to identify the object O. At the bottom of FIG. 3, the lightintensity is shown for the two views according to FIG. 3 at the top. Thelight flux is plotted on the ordinate, while the standardised lightguide coordinate is plotted on the abscissa. Curve 55 shows themeasurement of FIG. 3 at the top left, curve 56 the measurement of FIG.3 at the top right. A symmetrical view is shown with the two values onlybeing identical in the middle region, so that with difference formation,in the ideal case, a value of zero would emerge. The middle region isinitially insignificant, however, for identifying an object. If it isintended to also include this region, additional measurements can becarried out by a division of the light guides into a plurality of partsor by additional light-emitting diodes and photodiodes at the ends ofthe light guides, in order to also cover this region by additionalmeasured values.

Basically, the following problems are produced during the measurement:

If two light sources are used, for example in the form of LEDs, and areceiver according to the principle of EP 0 706 648 B1, the measuringmethod is insensitive with respect to temperature variations andnon-linearities on the receiving side owing to strong extraneous lightradiation in the receiving photodiode. On the transmission side, thedegree of efficiency of the LEDs influences the measuring result. As theequations G1) and G2) show, the absolute value of the LED degree ofefficiency is not entered, but only the ratio of the two values.

-   -   Measured signal of the receiver 1

$\begin{matrix}{U_{1} = {\frac{\eta_{L\; 1}}{\eta_{L\; 2}}K\frac{S_{1}}{S_{C\; 2}}}} & \left. {G1} \right)\end{matrix}$

-   -   Measured signal of the receiver 2

$\begin{matrix}{U_{2} = {\frac{\eta_{L\; 2}}{\eta_{L\; 1}}K\frac{S_{2}}{S_{C\; 1}}}} & \left. {G2} \right)\end{matrix}$wherein:

-   -   η_(L1)=transmission function transmitter 1    -   η_(L2)=transmission function transmitter 2    -   S_(C1)=optical damping factor compensation path transmitter 1    -   S_(C2)=optical damping factor compensation path transmitter 2    -   S₁=optical damping factor transmission path transmitter 1    -   S₂=optical damping factor transmission path transmitter 2    -   K=system constant.

Transmission paths are, for example, the paths entered in FIGS. 7 to 11along the arrows, while a compensation path is generally the path of thecompensation element to the receiver generally in the light guide. Ifthe light source 1 at the top left in FIG. 3 is the transmitter, thetransmitting path runs to the receiver Ea via the light guides 33, 34and the opening 11. The light source 2 at this moment is thecompensation element, so the compensation path runs from the lightsource 2 to the receiver Ea through the light guide 34.

When the two light-emitting diodes are subjected to uniform temperaturechanges, the measured value is therefore not influenced. However, as,the light sources 1, 2 may have different temperatures owing to theirlarge distance from one another, for example, in the application as ajamming protection, for example of a sliding roof, the measured valuemay be influenced by the temperature. This limits the absolute measuringprecision of the system.

Therefore, a dynamic measuring method is used currently, the mode offunctioning of which is based on detecting and evaluating rapid changeswith time constants that are smaller than the time constants which areconnected with temperature changes of the LEDs. If objects O are locatedfor a relatively long time in the light field of the monitoring region,it is difficult, however, to decide with the aid of a dynamicmeasurement whether the objects O are still present or not after arelatively long time.

It is therefore desirable to carry out a static measurement withabsolute precision and to suppress the temperature influence of thelight sources in the measuring result. This may, for example, take placewith the arrangement shown in FIG. 6. The method is based on carryingout two measurements with the different receiving elements Ea and Eb andusing the same transmitting elements 1 and 2 during the twomeasurements. The two measuring phases are activated sequentially by theprocessing unit 14 (for example a microprocessor). For the firstmeasurement, according to FIG. 3 at the top left, only the measuredsignal 28 is evaluated by the processing unit 14. The change-overswitches 15, 18, 19 are located in the position shown in FIG. 6 for thismeasurement.

The current sources or modulators 17 and 16 are modulated via thecentral clock generator of the clock circuit 13, the phase displacementbetween the two modulators being 180 degrees. In the case of rectangularmodulation signals, the light sources 1, 2 are thus switched on and offin an alternating manner and radiate their light into the lightconductors 33, 34. The receiver amplifier 6 with an optionally upstreamhigh pass filter amplifies the alternating component of thephotoelectric current generated by the receiver Ea, for example aphotodiode. In the synchronous demodulator 9, the amplified receivingsignal is separated into the two components, which were generated by thelight sources 1 and 2 and optionally switched via low pass filters. Thecomparator 8 evaluates the difference between the two receiving signalsand controls the current intensity of the modulator 16 in such a waythat the signal difference at the input of the comparator 8 becomeszero. The light source 1 is a compensation element at this moment.Alternatively, additional compensation elements may also be providedwhich do not depend on the light sources 1, 2, 3, 4. This manner ofobtaining a measured signal of a single measurement corresponds to theprior art according to EP 0 706 648 B1.

The current source 35 applies to the light source 1, 2, in addition tothe modulated current, an unmodulated direct current. It can thus beachieved that the compensation element is operated with the same currentas the light source 2. This is advantageous in order to keep the degreeof efficiency of the light sources constant between the twomeasurements.

The processing unit 14 stores the signal 28 in temporary storage. Thesecond measurement now takes place according to FIG. 3, top right, inthat the change-over switches 15, 18 and 19 are switched into the otherposition and the clock circuit 13 is activated. The light source 2 isadjusted by changing the current amplitude of the modulator 16 by thecontrol loop consisting of the receiver Eb, the receiver amplifier 22with an optionally upstream high pass filter, the synchronousdemodulator 23, optionally present low pass filters, the comparator 26and the modulator 16, 17 in such a way that the difference at the inputof the comparator becomes zero. When that has happened, the signal 27 isstored by the processing unit 14.

The signals 27, 28 are multiplied by the arithmetic unit 29 by means ofthe multiplier 36. As can be seen from the system equation G3), thisproduct is no longer dependent on the transmission function of thetransmitters, and therefore, in particular, the temperature dependencyof the transmitters or light sources 1, 2 is no longer significant inthe measured signal.

$\begin{matrix}{{U_{1}*U_{2}} = {K^{2}\frac{S_{1}S_{2}}{S_{C\; 1}S_{C\; 2}}}} & \left. {G3} \right)\end{matrix}$wherein:

-   -   η_(L1)=transmission function transmitter 1    -   η_(L2)=transmission function transmitter 2    -   S_(C1)=optical damping factor compensation path transmitter 1    -   S_(C2)=optical damping factor compensation path transmitter 2    -   S₁=optical damping factor transmission path transmitter 1    -   S₂=optical damping factor transmission path transmitter 2    -   K=system constant.

By comparing the product 30 with a static reference value, when thesliding roof closes, it can be identified whether an object O is locatedin the light field F. As the closing sliding roof amplifies the measuredsignal it may be sensible to store the reference value as acharacteristic curve which is dependent on the sliding roof position.This reference value characteristic curve can be adapted to soiling andageing influences by a learning run or adaptation method duringoperation. A static measurement is thus possible for whether an objectis currently moving in the light field F. Instead of or in addition tothe product, a division may also be carried out. The temperaturedependency would also be eliminated thereby.

In addition, the difference 31 between the signals 27 and 28 isgenerated by the arithmetic unit 29. This makes it possible to suppressthe interfering influence of the closing sliding roof on the measuredsignal. The difference is constant when the sliding roof is open andclosed and corresponds to a reference value, which is ideally zero.While the sliding roof is closing, a deviation of the difference valueoccurs according to the curve 51 in FIG. 4, from the reference value.This deviation again reduces to zero, however, when the sliding roof hasclosed. If a light field F is generated with a light intensitydecreasing along the light guide, an object O in the light field causesa deviation of the difference 31 from the reference value (FIGS. 4, 5).This deviation is all the greater the closer the object is located tothe closing edge 61 of the sliding roof. Thus it can be identified withthe aid of the trend of the difference 31 whether an object O is locatedin the sliding roof cutout when the sliding roof is closing, even whenthis object has been there for a relatively long time (staticmeasurement). If the light intensity in the region of the closing edgeaccording to FIG. 12 increases, the detection sensitivity increases; thedifference 31 is increased in the region of the closing edge 61 with thesame object size, and thus smaller objects can also be identified. Thisproduces the transmission/reception characteristic 60 shown in FIG. 12.For this purpose, the structure 40 at this location can becorrespondingly configured for corresponding configuration of anon-linear light gradient along the light guide. This static measurementonly requires one calibrating value, namely the difference 31 withoutthe object. This produces a substantially lower outlay for calibrationcompared to individual measurement or else product evaluation.

The static measurement during closing of the movable element 12 canadvantageously be switched off in favour of dynamic measurement, as inthis case it is ensured by the static measurement which is carried outuntil then, optionally in an alternating manner with the dynamicmeasurement, that no object is located in the light field F.Nevertheless, a static measurement, is basically also always possible,but optionally with an increased calibration outlay owing to themovement of the movable element 12, in other words, for example, thesliding roof.

FIG. 13 shows the signal course 71 at the closing edge 61 in thepresence of an object over the time. Without an object, the tolerancerange 70 exists. With the presence of an object, the signal changesuntil a static threshold 72 is exceeded. The dynamic measurement in theimage at the bottom also leads to a signal, as soon as the dynamicthreshold 73 is exceeded.

The difference 31 is not temperature-compensated. The temperature of thelight sources 1, 2 may be measured, however, via their forward voltagewhile being supplied with current. While the forward voltage is keptconstant by adaptation of the maximum transmitting current amplitude,the temperature influence of the transmitting diodes on the measuredsignal can also be compensated.

Basically, a plurality of light guides 34 a, 34 b can be provided alongat least one side of the opening. The light guides 33, 34 are arrangedalong the movement direction 39 of the movable part 12 and/ormirror-symmetrically to one another. If it is desired to achieve auniform light propagation, the structure 40 of the light guides can beprovided in an augmented and/or cumulative manner with increasingdistance from the transmitting element. The structure 40 is preferablyconfigured in such a way that the light intensity increases in theregion in which the movable part 12 is located at the end of its closingmovement. A motor drive 20 for the movable part 12 can be activated viathe signal 38.

A compensation element for extraneous light compensation by control ofthe light intensity radiated into the measuring arrangement by at leastone light source may be associated with the light guide 33, 34, so theclock-synchronous alternating light component which occurs betweendifferent phases of the light sources, becomes zero. The light sourcesare clocked here in a time-sequential manner and emit the lightphase-wise. The compensation element can be the light source 1, 2, 3, 4associated with the receiving light guide. The light source and receiverare connected to a control, with which the light signal of thelight-emitting diodes used as a light source are compensated with afurther modulated light signal in such a way that a constant lightsignal is substantially present at the receiver. In this case, thetemporal average value of the current, which is required to generate thefurther modulated light signal and/or the temporal average value of thecurrent, which is supplied to the at least one light-emitting diode canbe adjusted in such a way that they substantially correspond to oneanother.

The device is preferably associated with a vehicle sliding roof, awindow closer, a blind or part of a boot monitoring system. For ambientlighting, for example to emphasise the sliding roof by means of a lightring, the optic-fibre light guides 33, 34 may be at least partiallytransparent and the light may have a wavelength in a range which isvisible to the human eye. The clock frequency is generally a frequencywhich is not perceivable to the human eye. Alternatively, the lightguide may also be used, optionally via a further light source, asadditional lighting and be dimmed for emphasis, for example. This doesnot disrupt its use as jamming protection or an object identificationmeans, in particular when extraneous light compensation takes place atthe same time as the light of the further light source is then alsocompensated during the signal evaluation.

According to the method, to detect static changes, the signals presentat the receivers are multiplied by one another by means of a multiplier36 or alternatively divided by one another. The value thus obtained iscompared with a reference value, as is produced, in particular from thecurve 51. The reference value is preferably a characteristic curve setup via the movement path of the movable part 12, which is dependent uponthe position of the movable part. It is shown in FIG. 4 that, when anobject O is present, a deviation occurs which is not influenced by thesliding roof. When a difference value is generated, an object O whichhas also been located for a relatively long time in the opening is alsoidentifiable. FIG. 5, in particular, shows difference signals, withcurve 57 showing the difference signal on the basis of the reflection ofthe sliding roof and curve 58 the difference signal on the basis of anabsorbing object which is moving in the light field and is located infront of the edge of the closing sliding roof, in the light fieldsuperimposed with the influence of the sliding roof.

FIGS. 7 to 10 show various arrangements of the light sources 1, 2, byway of example, as transmitter and compensation element and thereceiver. While in FIG. 6, the light sources as the transmitter andcompensation element and also the two receivers are arranged diagonallyopposite with respect to the opening, in FIG. 7 the receivers are on oneend on the two sides of the opening and the two light sources on theother end. In this case, any desired arrangement of the light guides atthe edges of the opening is possible and, according to FIG. 8, the lightguides do not have to be the same length either.

In FIG. 9, the light sources, as transmitter and compensation element,are at a location along the light guides 33 a, 33 b or 34 a, 34 b or attheir transition region, corresponding input locations in the form ofbevels being provided. The receivers are arranged at the end of thelight guides 33 a, 33 b. Further receivers can also be provided at theother light guide 34 a, 34 b. The arrangement of the compensationelements and receivers is transposed in FIG. 10 compared to FIG. 9, sothe receiver Ea is arranged centrally between the light guides 33 a and33 b and further light sources 2, 3 are arranged at their ends. Ifnecessary, further light sources or receivers can also be provided here.In this case, it becomes clear that a light source or a receiver in anarrangement of this type can simultaneously be associated with aplurality of light guides. FIGS. 7 to 10 show only some possiblearrangements, but the person skilled in the art can discover furthersuitable arrangements, as long as various measurements are possible overthe opening.

Even the smallest signals can still be clearly detected owing to theextraneous light compensation known from EP 0 706 648 B1. Precipitationin the light field can also be sensed thereby, so a closing function canbe introduced as a result of the precipitation. The receiver can alsoperceive strong insolation in the region of the light field andthereupon initiate automatic closure of the movable part 12. Lightinformation about movements in the interior of a vehicle and/or on thewindows of a vehicle can be identified by means of the light guides andthe associated receivers Ea, Eb, so monitoring can simultaneously becarried out with the device.

The system is simultaneously very largely resistant to environmentalinfluences such as temperature, extraneous light, smoke, dust, fog,reflections, scratches on the light guide. System-dependent ageing ofthe part components or soiling in the region of the light guides canoptionally be counteracted by cyclic adaptation processes. Reflections,for example owing to the closing roof or the blind can be compensatedvia a learning run or adaptation method.

Owing to the sensitivity of the system, the legal requirements can besatisfied, in particular for the application purpose in the slidingroof, even if these system reaction times are such that, in the worstcase conditions, no jamming forces of >100 N are reached with a springrate of ≧10 N/mm or ≦65 N/mm in the opening region of 4 to 200 mm. Thesystem reaction time is therefore produced from the requirement toreliably identify a jamming with a spring rate of 65 N/mm, wherein itmust not exceed the maximally occurring jamming force 100 N. This hascorresponding consequences for the design of the system, in particularwith regard to the signal processing.

With regard to the system flexibility, system-relevant, vehicle-specificdata, such as light field geometries, roof cover etc. can beparameterised via an interface. Further parameters may be characteristicmaps for the vehicle speed, characteristic maps for the externaltemperature, characteristics maps for the triggering threshold (thesystem reaction time can thus be influenced, and thus the requiredjamming protection quality) and characteristic maps for detection as afunction of the blind or roof position. The robustness of the system canthus be increased.

The measuring precision can be increased by further measurements, inthat, for example, either the light guides are divided into a pluralityof light guides, or receivers and transmitters are provided at their twoends. As a result of this alone, for example, according to FIG. 11 anumber of eight measurements can be achieved with the bidirectionallight field in order to solve the resulting equation system. In thiscase, two light sources 1, 2 are arranged on one end of the lightguides, while at the respective other end of the light guides, areceiver Ea, Eb and a light source 3 or 4, in each case, are provided.If necessary, a further receiver could also be associated with the lightsources 1 and 2, in order to increase the number of possiblemeasurements.

In this case, the following eight fundamental equations are produced:

Measured signals of the first receiver Eb

$\begin{matrix}{U_{1a} = {\frac{\eta_{L\; 1}}{\eta_{L\; 2}}K\frac{S_{1}}{S_{C\; 2}}}} & \left. {G4} \right) \\{U_{1b} = {\frac{\eta_{L\; 1}}{\eta_{L\; 3}}K\frac{S_{1}}{S_{C\; 3}}}} & \left. {G5} \right) \\{U_{1c} = {\frac{\eta_{L\; 4}}{\eta_{L\; 2}}K\frac{S_{4}}{S_{C\; 2}}}} & \left. {G6} \right) \\{U_{1d} = {\frac{\eta_{L\; 4}}{\eta_{L\; 3}}K\frac{S_{4}}{S_{C\; 3}}}} & \left. {G7} \right)\end{matrix}$

Measured signals of the second receiver Ea

$\begin{matrix}{U_{2a} = {\frac{\eta_{L2}}{\eta_{L1}}K\frac{S_{2}}{S_{C1}}}} & \left. {G8} \right) \\{U_{2b} = {\frac{\eta_{L2}}{\eta_{L4}}K\frac{S_{2}}{S_{C4}}}} & \left. {G9} \right) \\{U_{2c} = {\frac{\eta_{L3}}{\eta_{L1}}K\frac{S_{3}}{S_{C1}}}} & \left. {G10} \right) \\{U_{2d} = {\frac{\eta_{L3}}{\eta_{L4}}K\frac{S_{3}}{S_{C4}}}} & \left. {G11} \right)\end{matrix}$wherein:

-   -   η_(L1)=transmission function transmitter 1    -   η_(L2)=transmission function transmitter 2    -   η_(L3)=transmission function transmitter 3    -   η_(L4)=transmission function transmitter 4    -   S_(C1)=optical damping factor compensation path transmitter 1    -   S_(C2)=optical damping factor compensation path transmitter 2    -   S_(C3)=optical damping factor compensation path transmitter 3    -   S_(C4)=optical damping factor compensation path transmitter 4    -   S₁=optical damping factor transmission path transmitter 1    -   S₂=optical damping factor transmission path transmitter 2    -   S₃=optical damping factor transmission path transmitter 3    -   S₄=optical damping factor transmission path transmitter 4    -   K=system constant

The following combinations of the fundamental equations G4 to G11 areindependent of the degree of efficiency of the transmitters, so thetemperature dependency of the transmitting elements is again compensatedin the measurements:

$\begin{matrix}{{U_{1b}*U_{2c}} = {K^{2}\frac{S_{1}S_{3}}{S_{C\; 1}S_{C\; 3}}}} & \left. {G12} \right) \\{{U_{1c}*U_{2b}} = {K^{2}\frac{S_{4}S_{2}}{S_{C\; 4}S_{C\; 2}}}} & \left. {G13} \right) \\{{U_{1a}*U_{2a}} = {K^{2}\frac{S_{1}S_{2}}{S_{C\; 1}S_{C\; 2}}}} & \left. {G14} \right) \\{{U_{1d}*U_{2d}} = {K^{2}\frac{S_{3}S_{4}}{S_{C\; 3}S_{C\; 4}}}} & \left. {G15} \right)\end{matrix}$

The measuring sequence is as follows here:

-   1) Generation of the signal U_(1a):

The light of the light source 1 and the light of the light source 2 arereceived via the receiver Eb. The receiving signal, which generates thelight source 1 in the receiver Eb, is compared with the receivingsignal, which the light source 2 produces in Eb. By means of outputcontrol of the light source 2, the light output is adjusted such thatthe same signal is received at the receiver E1 from the two lightsources 1 and 2. The measuring signal U_(1a) is proportional to thetransmission output of the light source 2.

The other measured signals are obtained in an analogous manner, withfour measurements being produced for each receiving element from thecombination of the two transmitting elements or light sources 1, 2, 3, 4on the transmitting light guide side and the two transmitting elementsor light sources 1, 2, 3, 4 on the receiving light guide side. The lightsource, which is controlled with respect to its light output, willhereinafter be called the compensation element.

-   2) Generation of the signal U_(1b):    -   Light source 1: transmitting element    -   Light source 3: compensation element    -   Eb: receiver-   3) Generation of the signal U_(1c):    -   Light source 4: transmitting element    -   Light source 2: compensation element    -   Eb: receiver-   4) Generation of the signal U_(1d):    -   Light source 4: transmitting element    -   Light source 3: compensation element    -   Eb: receiver-   5) Generation of the signal U_(2a):    -   Light source 2: transmitting element    -   Light source 1: compensation element    -   Ea: receiver-   6) Generation of the signal U_(2b):    -   Light source 2: transmitting element    -   Light source 4: compensation element    -   Ea: receiver-   7) Generation of the signal U_(2c):    -   Light source 3: transmitting element    -   Light source 1: compensation element    -   Ea: receiver-   8) Generation of the signal U_(2d):    -   Light source 3: transmitting element    -   Light source 4: compensation element    -   Ea: receiver

The products U_(1b)*U_(2c), U_(1c)*U_(2b), U_(1a)*U_(2a) andU_(1d)*U_(2d) no longer contain any dependency on the transmissionfunctions η_(L1), η_(L2), η_(L3), η_(L4) of the transmitting elements,resulting, in particular, in a temperature influence owing to atemperature difference between the transmitting element and compensationelement being eliminated.

It is obvious that this description can be subjected to the most variedmodifications, changes and adaptations which vary in the range ofequivalents to the annexed claims.

LIST OF REFERENCE NUMERALS

-   1, 2, 3, 4 light source-   6, 22 receiver amplifier-   8, 26 comparator-   9, 23 synchronous demodulator-   11 opening-   12 movable part-   13 clock circuit-   14 processing unit-   15, 18, 19 change-over switch-   16, 17 modulator-   20 motor drive-   27, 28 signal-   29 arithmetic unit-   30 product-   31 difference-   32 control unit-   33 first light guide-   34 further light guide-   34 a, 34 b plurality of light guides-   35 current source-   36 multiplier-   37 difference generator-   38 control signal-   39 movement direction-   40 structure-   51, 52, 53 curve-   54 light path-   55 . . . 58 curve-   60 transmitting/receiving characteristic-   61 closing edge-   70 tolerance band without object-   71 signal characteristic curve over the time-   72 static threshold-   73 dynamic threshold-   Ea, Eb receiver-   F light field-   O object

1. A device for identifying an object in or on a closable opening,comprising a device for opening and closing the opening by means of amovable part and an optoelectronic detection mechanism for identifyingthe object, which feeds light into at least one first light guide and atleast one second light guide by means of at least one light source anddetects changes in the received light by means of at least one receiver,wherein each of the first light guide and the second light guide has ameans for emitting light transversely to its longitudinal extent and ameans for receiving light transversely to its longitudinal extent, whilebeing in operative connection with the at least one receiver, whereinthe first and second light guides are arranged at the edge of theopening in such a way that a bidirectional light field is producedbetween them which at least partially bridges the opening, wherein aclock circuit is provided, which feeds light in an alternating mannerinto the first and second light guides, which light is received by theat least one receiver, and wherein a comparison means is provided forcomparing the signals present at the at least one receiver to identifythe object.
 2. The device according to claim 1, wherein the opening isan opening of a vehicle.
 3. The device according to claim 1, wherein amultiplier or a divider is provided for temperature compensation, whichmultiplies or divides the signals present at the at least one receiverby one another to identify changes, and wherein a control unit comparesthe product or the division result with a reference value.
 4. The deviceaccording to claim 3, wherein the reference value is a characteristiccurve which is set up by means of a movement path of the movable part,and depends on a position of the movable part.
 5. The device accordingto of claim 1, wherein a difference generator is provided foridentifying an object located in the bidirectional light field andgenerates a difference from the signals present at the at least onereceiver.
 6. The device according to claim 1, wherein the first andsecond light guides are provided on opposing sides of the opening. 7.The device according to claim 1, wherein a plurality of first or secondlight guides are provided along a side of the opening.
 8. The deviceaccording to claim 1, wherein the first and second light guides arearranged along a movement direction of the movable part and/ormirror-symmetrically.
 9. The device according to claim 1, wherein thefirst and second light guides each have a structure for radiating out orreceiving the light transversely to their longitudinal direction. 10.The device according to claim 9, wherein the structure is provided in anaugmented and/or cumulative manner, with increasing distance from thelight source.
 11. The device according to claim 9, wherein the structureis configured such that it increases the light intensity in a region inwhich the movable part is located at the end of its closing movement.12. The device according to claim 1, wherein a motor drive is providedto move the movable part, which motor drive is activated as a result ofthe signals present at the at least one receiver.
 13. The deviceaccording to claim 1, wherein a measuring arrangement comprising thefirst and second light guides, the at least one light source, and the atleast one receiver is provided, and wherein a compensation element forextraneous light compensation by control of the light intensity radiatedinto the measuring arrangement by the at least one light source isassociated with the first and second light guides, so that a clockedalternating light component, which occurs between different phases ofthe light alternately emitted into the opening by the first and secondlight guides, becomes zero, wherein the at least one light source emitslight in a phase-wise manner and clocked in a time-sequential manner.14. The device according to claim 13, wherein the compensation elementis the light source associated with the receiving one of the first andsecond light guides.
 15. The device according to claim 1, wherein the atleast one light source and the at least one receiver are connected to acontrol, with which the light signal of a light-emitting diode used asthe light source is compensated with a further modulated light signal insuch a way that a constant light signal is substantially present at thereceiver, wherein the temporal average of the current, which is requiredto generate the further modulated light signal, and/or the temporalaverage of the current which is supplied to the light-emitting diode,substantially correspond to one another.
 16. The device according toclaim 1, wherein the device is associated with a sliding vehicle roof ora window closer or a blind or is part of a boot monitoring system.
 17. Amethod for identifying an object in or on an opening which can be closedby means of a movable part, comprising the steps of: arranging aplurality of light guides along the opening including at least one firstand at least one second light guide, wherein each of the first lightguide and the second light guide has a means for emitting lighttransversely to its longitudinal extent and a means for receiving lighttransversely to its longitudinal extent; emitting light in analternating manner from the at least one first light guide transverselyto its longitudinal extent and then the at least one second light guidetransversely to its longitudinal extent to form a bidirectional lightfield at least partially bridging the opening; receiving light emittedfrom one light guide by means of at least one receiver that is inoperative connection with the other light guide; and comparing thesignals present at the at least one receiver to identify the object. 18.The method according to claim 17, characterized in that, to identifychanges, the signals present at the receiver are multiplied by oneanother or divided and are compared with a reference value.
 19. Themethod according to claim 18, wherein a characteristic curve set up bymeans of a movement path of the movable part is stored as the referencevalue and is dependent on the position of the movable part.
 20. Themethod according to claim 17, wherein a difference is generated from thesignals present at the receiver to identify an object located staticallyin the light field.
 21. The method according to claim 17, wherein thelight intensity of the light emitted from the light guides is increasedin the region in which the movable part is located at the end of itsclosing movement.
 22. The method according to claim 17, wherein theopening with the movable part is closed by a motor drive, which isactivated as a result of the signals present at the receiver.
 23. Themethod according to claim 17, wherein the object is a precipitation, andthe opening is closed on identification of the precipitation.
 24. Themethod according to claim 17, wherein the light guides are partiallytransparent, and light is radiated into the light guides in a wavelengthrange which is visible to the human eye and preferably at a frequencywhich is not perceivable to the human eye.
 25. The method according toclaim 17, wherein the receiver senses strong insolation in the region ofthe light field, and thereupon initiates automatic closing of themovable part.
 26. The method according to claim 17, wherein the movablepart is a vehicle part.
 27. The method according to claim 17, whereinincident light in the second light guide contains light informationabout movements in an interior of a vehicle and/or at the windows of thevehicle, which information can be evaluated by an evaluation unit. 28.The method according to claim 17, wherein the light signal of onelight-emitting diode used as the light source is compensated with afurther modulated light signal in such a way that substantially aconstant light signal is present at the receiver, wherein the temporalaverage of the current, which is required to generate the furthermodulated light signal, and/or the temporal average of the current whichis supplied to the light-emitting diode, is changed in such a way thatthe temporal averages substantially correspond.